Foldable step



March 25, 1947. MCFARLAND 2,417,987

FOLDABLE STEP Filed Nov. 15, 1944 INVENTQR Donald L'Jllcibrland ATTORNEY' Patented Mar. 25, 1947 FOLDABLE STEP Donald L. McFarland, Milford,Conn, assignor to United Aircraft Corporation, East Hartford, Conn, acorporation of Delaware Application November 16, 1944, Serial No.563,775

11 Claims.

1 This invention relates to a foldable step for streamlined vehiclebodies and has particular reference to an improved foldable step for usein entering and leaving the cockpit of an airplane.

An object of the invention is to provide an im proved vehicle cockpitstep of the type which swings between an extended operative position anda folded inoperative position in which latter position it is concealedwithin the vehicle body and forms a. part of the exterior surface orskin so that the latter presents a smooth surface having a minimum ofsurface drag.

A further object of the invention is to provide a foldable step of thisgeneral type which is normally biased into concealed position and havingfoot operative means associated therewith for moving the steptemporarily into an extended position.

A still further object of the invention is to provide a foldable stepwhich is entirely foot operated and is disposed in its folded positionwholly within the inter-frame space in the vehicle frame withoutprojecting inwardly beyond the frame.

Other objects and advantages of the invention will appear from thefollowing detailed description of a preferred embodiment thereof,considered in connection with the accompanying drawing which issubmitted for purposes of illustration.

In the drawings,

Fig. l is a rear view of a portion of an airplane fuselage havinginstalled therein a foldable step embodying the present invention, thestep being shown in folded position and certain parts bein broken awayto facilitate illustration.

Fig. 2 is a section on line 2-2 of Fig. 1.

Fig. 3 is a view illustrating the adjustable stop structure forarresting the step in its folded position.

Fig. 4 is a section on line 44 of Fig. 1, and

Fig. 5 is a section on line 5-5 of Fig, 1.

Referring particularly to Figs. 1 and 2, l0 and I2 indicate portions ofadjacent curved frames of an airplane fuselage structure, at one side ofthe fuselage, between which an outwardly swingable step S and aninwardly swingable door D are pivotally mounted, together with certainmechanism hereinafter described for operatively connecting the two.

The frames H] and I2 comprise special channel.

sections disposed back to back. As shown in Fig. 4, each of thesechannels comprises parallel legs 14 and Hi, the latter having aninturned flange portion l8 which lies parallel with the back 20 of thechannel. The unfianged legs l4 of the frames provide the outer curvedsurface of the frame on which the skin 22 of the fuselage is secured. Agenerally rectangular opening .24 is provided in the skin between framesI0 and 12 to accommodate the foldablestep S and the door D immediatelyabove it, this opening extending almost the entire distance between thebacks 20 of the channels 10 and l2.

Slightly below the lower edge 26 of opening 24,

the frames 10 and I2 are connected by an intercostal member 28 having atransverse web portion 30 which extends from back to back of thechannels and has depending ear 32 which are secured by rivets 34 to thebacks 20 of the channels. Frame member 28 also has a depending frontapron 36 which extends across the opening between the channels and isdisposed in the plane of the legs 14 of said channels and constitutesthe support for the edge of the skin along the lower edge 26 of the skinopening 24, suitable rivets 38 having their heads flush with the outersurface of the skin being provided to connect the skin to apron 36. Theframe member 28 also has an upstanding rear apron 40 which is disposedin the plane of the legs iii of channels 10 and I2 and, among otherthings, constitutes the bearing surface for an inner closure plate 42which covers the inter-rib space between the channels.

The plate 42 overlies the inner surfaces of legs 16 and is securedremovably thereto by a series of screws 44 which extend through theplate and the legs 16 and are screw threaded into nut plates permanentlysecured to the inner faces of channel legs iii. In order to providesuflicient space to receive these nut plates the flanges [8 are rolledoutwardly into the plane of legs l6 for a distance along the framemembers slightly greater than the height of the plate as is clearlyshown in Fig. 1.

An intercostal member 48 similar to member 28 is disposed between theframes l0 and I2 above the upper edge 50 of the skin opening 24. Thisintercostal member has upwardly extending ears 52 overlying the backs 20of the frames and secured thereto by rivets 54 and also has aprons 56and 58 which lie respectivelyv within the planes of channel legs 14 andI6. Apron 56 is secured to the skin 22 by rivets 5B. The plate 42 issecured at its lower and upper edges to aprons 40 and 58 by screws 62which are screw threaded into nut plates 64 and 66. The nut plates 64are permanently secured to the outermost surface of apron 58 while thenut plates 66 are secured to the corresponding surface of a cross bar 68of a U-shaped supportin bracket. In addition to the cross bar 68 thisbracket has parallel generally rectangular end plates I which overliethe backs 20 of channels I0 and I2 and are riveted thereto by rivets I2.g

The step S is a hollow casting having end walls I3 generally triangularin section, a fiat transversely ridged tread portion I4, a bottomportion 16 which is slightly curved to conform to the normal skincontour of the fuselage, and a short heel portion I8, which forms anabutment adapted to seat against the inner surface of bar 60 when thestep is in its open position shown dotted in Fig. 3.

The step is pivoted adjacent the junction of its heel and tread portionson short bolts 80, which extend through the back 20 of each of thechannel members It and I2 and through the adjacent plates I0; Each ofthese bolts has a sleeve 82 which is of approximately the length of athickened portion 84 of the step end walls, nuts 86 serving to hold thespacing sleeves 82 in position on the bolts. v

The stepS is also providedwith intermediate flanges 88 in which ismounted a spring supporting rod 90 for a torsional spring 92. Thisspring'has parallel arms 94 extended beneath the tread portion of thestep and an intermediate, oppositely extended loop portion 98 hearingagainst the bar 68 in such manner that the step S is constantly biasedinto its closed position shown in Fig. 2 in which its curved bottomsurface I6 forms a continuation of the skin surface 22. As shown in Fig.3, a nut plate 98 is secured to the outstanding leg of an angle memberl00'which is riveted to the back 20 of channel frame II). This nut has astop bolt I02 screw threaded therein, the head I04 of which engages thetread 'of the step in its folded position, thus providing an accuratelyadjustable stop for positioning the surface I6 flush with the skin inthe normal position of the step.

The step S occupies somewhat more than onehalf the height of the opening24. The remainder of the opening above it is closed by the door D whichhas a suitable curvature to conform to the skin contour of the fuselage.The door comprises an inner plate member I05 of a width slightly greaterthan the width of opening 24, as is clearly illustrated in Fig. 1,having cut outs I01 and having an outer plate member I08 riveted theretoby rivets H8 at the lower edge thereof and by rivets H2 at the upperedge. The door D is hinged adjacent its upper end to swing inwardly bytwo complemental piano hinge memhers I I4 and N6 the former of which isconnected to the web 48' and the other of which is secured by rivets II2to the door. A torsional spring is provided on a rod II8 mounted in abracket I28 and has its oppositely extending spring arms I22 and I24abutting the inner surface of the door and the web 48 respectively toconstantly bias the door outwardly to position the overlapping sideedges I26 of the inner door plate I06 against the inner surface of theskin 22 along the side margins of the opening 24.

The door D and the step S'are operatively connected by a cam lever I20which has an integral outer sleeve I30 journalled on a bolt I32 securedto the back 20 of channel I2. This lever has an upper nose portion I34which engages the inside of door plate I06 and has a dependingcam'portion I36 which overlies the inner surface of the tread portion 14of the step in the normal position thereof. The member I28 is biasedinto the above described position by a torsional spring I38 which hasone end I40 thereof hooked over the back of the cam lever and the otherend I42 hooked through an aperture in the back 20 of channel I2 so thatmember I28 is constantly biased in a counter-clockwise direction asviewed in Fig. 2.

When it is desired to climb in or out of the cockpit, the pilot merelypushes the door in with the toe of the foot on which he is about tostep. The inward movement of the door D rotates the cam lever I28 in aclockwise direction, as viewed in Fig. 2, and the cam portion I30thereof moves the step S in a counter-clockwise direction into apartially extended position so that upon a natural downward movement ofthe pilots foot the door will move to the dotted fully open position, asshown in dotted lines in Fig. 3. As soon as the pilot removes his footfrom the step the latter will return to its concealed position,abuttingthe head I04 of stop bolt I02 against which it is held by therelatively heavy spring 92. having returned to its normal position assoon as the pilot steps down onto step S, the parts are again in theirnormal position in which the outer surface contour of the fuselage isun-- broken.

It will be evident from the above description that this inventionprovides a foldable step suitable for use in aircraft fuselage, or anyother streamlined vehicle body, which occupies a minimum of space Withinthe body frame structure and which preserves the outer streamlinedcontours of the body. It will further be evident that the improved stepconstruction is both convenient to use and simple and inexpensive to'manufacture.

Further by reason of the operative connection between the entrance doorand the step the previous difficulties with steps of this generaltype inwhich the pilot was obliged to unfold the step by a downward and outwardmotion of his foot has been entirely eliminated.

While I have shown what is believed to be a preferred embodiment of myinvention in connection with an airplane fuselage it will be evidentthat various changes in the construction and arrangement of the partsmay be made without exceeding the scope of the invention and, further,that the invention is applicable to many uses outside of the aircraftfield.

I claim:

1. In a streamlined body having a step-opening in a side thereof, a-steppivotally mounted in said opening adjacent the lower margin thereof andswingable between a concealed position within said body in which itforms a flush closure for a lower portion of said opening and anoperative position in which it extends laterally therefrom, means forbiasing said step into concealed position, a door pivotally mountedadjacent the upper margin of said opening forming a closure for an upperportion of said opening and swingable into said body, means for biasingsaid door into a posi-' tion in which it is flush with the surface ofsaid body and means responsive to 'inward pivotal movement of said doorfor moving said step toward its operative position.

2. In a streamlined body having a step-opening in a side thereof, a stephaving a tread pivotally mounted in said opening adjacent the lowermargin thereof and swingable between a concealed position within saidbody in which it forms The door D.

a-flu'sh closure for alowerportio'n of said opening-r andwa'noperativeiposition in which it extends step toward its" operativeposition when said door is swung inwardly;

J 3. In a streamlined body having a step-openingin aside thereof, a stephaving a tread pivotally mounted in said opening adjacent the lowermarginthereof' and swingable betweena concealed position within saidbody in which it forms a flush closure for a lower portion of saidopening andan operative position in which it extends laterallytherefrom, means for biasing said' step into concealed position, a doorpivotally mounted adjacent the upper marginof said opening and swingableinto said body, means for biasing said door into a position inwhi'ch' itis flush with the surfaces of said body, and pivoted means actuated byinward movement of said. door'for simultaneously moving said stepoutwardly.

4. In an'airplane having a frame and a skin covering'said frame, saidskin having a stepopening therein and said frame including supportingmeans adjacent said opening, a step supported' on' said supporting meansand having a pivotal connection therewith, said step being spring.biased into a concealed position within said frame wherein it fills alower portion of said opening and presents a surface continuous with theskin surface, a door supported on said supporting means and having apivotal connection therewith, said door being spring biased into aposition in which it prevents a surface continuous with the skin surfaceand being movable inwardly from said position into said airplane, and acam lever having a pivotal support intermediate its ends on said frame,said lever having a portion disposed in the path of said door when thelatter moves inwardly and a portion disposed behind said step at a pointremote from the pivotal support for the latter for swinging said stepoutwardly simultaneously with inward movement of said door.

5. In an airplane, a frame including a pair of spaced rib members and askin covering the outer surfaces of said ribs, said skin having astepopening therein and said frame having supporting means adjacent theupper and lower margins of said opening, a step supported on thesupporting means adjacent said lower margin and having a pivotalconnection therewith, said step being spring biased into an inoperativeposition within said frame wherein it fills a lower portion of saidopening and presents a surface continuous with the skin surface, a doorsupported on said supporting means adjacent said upper margin and havinga pivotal connection therewith, said door being spring biased into aposition in which it presents a surface continuous with the skin surfaceand being movable inward- 1y from said position into the space withinsaid frame, means having an operative connection with said door formoving said step toward its operative position in which it projectsoutwardly from said opening upon inward movement of said door, and aninner skin covering the inner surfaces of said ribs in the vicinity ofsaid opening.

6. In an airplane, a frame including a pair of spaced rib memberscomprising channel members disposed back'to back, an outer: skin.covering the frame -andiattached to. the .outer channel legs; said skinhaving astep-opening between said ribs, an 'inner'skin member ,coveringthe frame in the vicinity of said opening and attached to the. innerchannel legs thereof and defining an intercostal step receiving spaceback of said opening, a step pivotally connected to said frame adjacentthe lower margin of said open- 1 ing and swingable between aninoperative position in which it is disposed wholly within said spaceand presents an outer surface continuous with the skin surface over alower'portion of said opening and an operative position in which it :2projects substantially horizontally from said opening, a door pivotallyconnected to said frame adjacentthe upper margin of said opening andswingable into said space, means for biasing said doorinto a normalposition in which it presents an outer surface flush with said outerskin over the remainder of said opening, means for biasing said stepinto inoperative position, and means'operatively connecting said doorand step for moving the latter toward operative position by the inwardmovement of said door.

7'. In an airplane having a frame and a skin covering said'frame, saidskin having a stepopening therein, a step pivotally connected to saidframe adjacent the-lower margin of said opening and swingable between aninoperative position in which it is disposed wholly within said frameand an operative position in which it projects substantiallyhorizontally from said opening, a door pivotally connected to said frameadjacent the upper margin of said opening and swingable inwardly, meansfor biasing said door for outwardly swinging movement, means for biasingsaid step for inwardly swinging movement, means responsive to inwardpivotal movement of said door for moving said step toward its operativeposition, and means for arresting the movement of said door and saidstep in the direction of their bias so that both present an externalsurface flush with the skin surface and completely closing said opening.

8. In a vehicle body having a cockpit enclosed by a frame and having anouter skin provided with an opening therein between frame members,mechanism for facilitating the entry of a passenger into said cockpitover the side of said vehicle body, said mechanism being operated by acombined inward and downward movement of the passengers foot andincluding, a movable step member normally biased into an inoperativeposition in which it forms a closure for the lower portion of saidopening, an upper member forming a closure for the remainder of saidopening having a portion immediately above said step member which isengageable by the passengers foot and is movable inwardly by the inwardmovement of the passengers foot, and means responsive to inward movementof said upper closure member for moving said step member into aprojected position in which it is engageable upon the downward movementof the passengers foot.

9. In a vehicle body having a frame and an outer skin provided with anopening therein between frame members, a step pivoted to said body andswingable between an operative position in which it projects outwardlybeyond said skin and an inoperative position in which it forms a closurefor the lower portion of said opening, a door pivoted at its upper endto said body adjacent the upper end of said opening and swingablebetween .an inoperative position. in which; it forms a closure for theremainder of said opening and an operativepositionin which it projectsinto said body, and means responsive to pivotal movement of said doorinto said body for initiating movement of said'step into its operativeposition. I

10. In a vehicle body having spaced rib members and a skin on the outersurfaces of said members, said skin having an opening therein betweenadjacent membersastep pivotally supported on said body and swingablebetween an operative positionin which it projects outwardly beyond saidskin and a normal inoperative position in which it forms a closure forthe lower portion of said opening, a door pivoted to said bodynear theupper end of said opening and swingablebetween an operative position inwhich it projects within said body and an inoperative position in whichit forms a closure for the remainder of said opening, means for biasingsaid door and said step into their inoperative positions, a skin on theinner surfaces of said rib members back of said opening forming ashallow 8 v of a passenger into said cockpit over the sideoi said bodywhich is operated by the inward and downward movement of the passenger'sfoot in-' cluding, a step pivoted to said body andswingable between anoperative position in which it projects outwardly from said skin and aninoperative position in which it forms a closure for the lower portionof said opening, ,a door pivoted turning said step to its inoperativeposition upon removal of the passenger's foot.

DONALD L, McFARLAND.

REFERENCES CITED 9 The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,378,713 Nami May 17, 19212,158,949 Sarles et a1. May 16, 1939 1,621,479 Cleveland et a1. Mar. 15,1927 1,877,152 vogel Sept. 13, 1932 1,817,921 Knaggs Aug, 11, 1931,

